前言
    在深基础施工中，经常需要降低地下水位，而国内常用的轻型井点，存在一些难以克服的缺点，其性能也是不理想的。轻型井点受吸程限制，如果降水深度超过6m，往往需要设置多级井点，至使抽水设备翻番，挖土量也明显增加，轻型井点并距很小，土方运输车辆和施工机械出入不便，而且施工费用也高。1983年，我局在承建引滦入津工程时，大面积的基坑降水，若采用轻型井点，需设置1万5千口以上井点，保证降水系统的正常运转是比较困难的。繁重的施工任务促使我们探索降水新技术，经过试验验证，决定采用深井井点，全部基坑只需600口井点即可满足降水要求，降水深度可以超过10m。潜水泵出现故障，只局限于单个的井点，更换也比较方便。深井井点在引滦入津工程中的成功应用，表明其性能优于国内认为先进的喷射井点，该项技术在我局承建的国内外工程中都已得到推广应用。微透水性土层历来都是降水的难题，近年来在天津地区采用深井井点降水取得成功，使降水技术又取得了新的进程。
1特点及适用范围
    1．l特点
    深井井点降水是将潜水泵沉入井管底部，将水排出，故不受吸程限制，一般可根据需要的降水深度确定井深和井距，深井井点管路没有严格的密闭要求，安装维修都比较方便，而且费用和能耗都较低。
    1．2适用范围
    深井井点降水适用于渗透系数在10m／ed以上的土层。天津地区的土层渗透系数很小，但有一定数量的透水类层。故也能有效地降低地下水位，但需延长抽水时间，安排基坑开挖应考虑提前降水时间。
2材料
    2．1滤管
采用无砂砼管作滤管。
2．2滤网
宜采用双层滤网，内层用筛网号2.5－l.24（0.24－40.96孔/cm2，即8－16目）尼龙丝筛网，外层用尼龙或塑料窗纱（约1.6mm孔），滤网也可用双层棕皮代替。
2．3滤料
宜采用粗砂或3－8mm砂砾混合料，要求滤料级配合理，孔隙率较小。
3施工准备
3．l机具准备
以一台钻机配备考虑；
Preface
    In deep foundation construction, it is often necessary to reduce groundwater levels, and domestic common light well, there are some difficult to overcome the shortcomings, the performance is not satisfactory. Light well by the suction limit, if the rainfall depth of more than 6m, often need to set up multi-level wells, pumping equipment to make double the amount of excavation has also increased significantly, from the light well and a small, earth-moving transport vehicles and construction machinery access inconvenience, but construction costs are high. In 1983, the Bureau Luan River to Tianjin in the construction of projects, large areas of the foundation pit, the use of a light well, needs to be set 10 005 1 000 or more wells to ensure the normal operation of precipitation systems is difficult. Heavy precipitation in the construction task prompted us to explore new technology, after experimental verification, decided to use deep well point, all pit only 600 wells can meet the requirement of precipitation and precipitation depth of more than 10m. Submersible pump failure is confined to individual wells, the replacement is relatively easy. Deep well point in Luan River to Tianjin project successful application, show that its performance is superior to the domestic advanced injection wells that point, the technology at home and abroad in the construction of our Bureau projects have been promoted and applied. Micro-porous layer has always been the problem of precipitation in recent years in Tianjin with the success of Deep Well, so precipitation technology has made new progress.
Features and application 1
    1. l Features
    Deep Well Submersible Pump is to sink tube wells the bottom of the water discharge, it is not subject to restrictions on smoking process may generally be required to determine the depth of precipitation from the well depth and well, deep well point pipe is not strictly confined requirements, installation and maintenance are more convenient, and cost and energy consumption is relatively low.
    1.2 Scope
    Deep Well for the permeability of soil in 10m/ed above. Permeability of soil in Tianjin area is small, but there are a number of permeable type layer. It also can effectively reduce the water table, but need to extend the pumping time for the excavation should be considered ahead of time of precipitation.
2 Materials
    2.1 Filter Pipe
Concrete pipe used for non-sand filter tube.
2.2 Filter
Should adopt the double filter, the inner sieve No. 2.5-l.24 (0.24-40.96 holes / cm2, the 8-16 mesh) nylon screen, the outer layer of nylon or plastic window screening (about 1.6mm hole) , the filter can also be used instead of double brown leather.
2.3 filter
Should use sand or 3-8mm gravel mixture, with the reasonable demands filter level, low porosity.
3 construction preparation
3. l machines ready
Drilling rig equipped with a consideration;